import java.util.Scanner;
public class calculator {
    public static void main(String[] args){
        double a,b,c,d;
        int op;
        Scanner reader = new Scanner(System.in);
        System.out.println("输入a:");
        a = reader.nextDouble();
        System.out.println("输入b:");
        b = reader.nextDouble();
        System.out.println("输入1.+,2.-,3.*,4./");
        op = reader.nextInt();
        switch (op)
        {
            case 1:System.out.println(a+b);
                   break;
            case 2:System.out.println(a-b);
                   break;
            case 3:System.out.println(a*b);
                   break;
            case 4:System.out.println(a/b);
        }
    }
}
